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simple_nc4_rd.c
/* Copyright 2019 University Corporation for Atmospheric
Research/Unidata. See COPYRIGHT file for conditions of use. */
#include <stdlib.h>
#include <stdio.h>
#include <netcdf.h>
/* This is the name of the data file we will read. */
#define FILE_NAME "simple_nc4.nc"
/* We are reading 2D data, a 6 x 12 grid. */
#define NX 6
#define NY 12
/* Handle errors by printing an error message and exiting with a
* non-zero status. */
#define ERRCODE 2
#define ERR(e) {printf("Error: %s\n", nc_strerror(e)); exit(ERRCODE);}
int
main()
{
/* There will be netCDF IDs for the file, each group, and each
* variable. */
int ncid, varid1, varid2, grp1id, grp2id;
unsigned long long data_in[NX][NY];
/* Loop indexes, and error handling. */
int x, y, retval;
/* The following struct is written as a compound type. */
struct s1
{
int i1;
int i2;
};
struct s1 compound_data[NX][NY];
/* Open the file. NC_NOWRITE tells netCDF we want read-only access
* to the file.*/
if ((retval = nc_open(FILE_NAME, NC_NOWRITE, &ncid)))
ERR(retval);
/* Get the group ids of our two groups. */
if ((retval = nc_inq_ncid(ncid, "grp1", &grp1id)))
ERR(retval);
if ((retval = nc_inq_ncid(ncid, "grp2", &grp2id)))
ERR(retval);
/* Get the varid of the uint64 data variable, based on its name, in
* grp1. */
if ((retval = nc_inq_varid(grp1id, "data", &varid1)))
ERR(retval);
/* Read the data. */
if ((retval = nc_get_var_ulonglong(grp1id, varid1, &data_in[0][0])))
ERR(retval);
/* Get the varid of the compound data variable, based on its name,
* in grp2. */
if ((retval = nc_inq_varid(grp2id, "data", &varid2)))
ERR(retval);
/* Read the data. */
if ((retval = nc_get_var(grp2id, varid2, &compound_data[0][0])))
ERR(retval);
/* Check the data. */
for (x = 0; x < NX; x++)
for (y = 0; y < NY; y++)
{
if (data_in[x][y] != x * NY + y ||
compound_data[x][y].i1 != 42 ||
compound_data[x][y].i2 != -42)
return ERRCODE;
}
/* Close the file, freeing all resources. */
if ((retval = nc_close(ncid)))
ERR(retval);
printf("*** SUCCESS reading example file %s!\n", FILE_NAME);
return 0;
}
nc_close
EXTERNL int nc_close(int ncid)
Close an open netCDF dataset.
Definition dfile.c:1334
nc_open
EXTERNL int nc_open(const char *path, int mode, int *ncidp)
Open an existing netCDF file.
Definition dfile.c:698
nc_inq_ncid
EXTERNL int nc_inq_ncid(int ncid, const char *name, int *grp_ncid)
Return the group ID for a group given the name.
Definition dgroup.c:56
nc_inq_varid
EXTERNL int nc_inq_varid(int ncid, const char *name, int *varidp)
Find the ID of a variable, from the name.
Definition dvarinq.c:60
nc_get_var
EXTERNL int nc_get_var(int ncid, int varid, void *ip)
Read an entire variable in one call.
Definition dvarget.c:1038
netcdf.h
Main header file for the C API.
NC_NOWRITE
#define NC_NOWRITE
Set read-only access for nc_open().
Definition netcdf.h:135